1. Field of the Invention
The present invention relates to surgery using a robot, and more particularly, to a method and a system for cutting the knee joint using a robot, wherein a surface, on which an artificial joint is to be coupled to the knee joint, can be formed with maximum safety and high precision in implementing total knee replacement arthroplasty while minimizing the incision, of the skin by the robot without causing damage to the tissue around the patella.
2. Description of the Related Art
These days, as old age population increases, arthritis and osteoporotic hip fracture tend to increase.
In this regard, by directly implementing knee replacement arthroplasty rather than using an indirect therapy such as parmacotherapy, physical therapy and intra-articular injection therapy, which is mainly used in the past, early mobilization is enabled without pain. Also, with the development of joint mechanics, the lifetime of an artificial joint is increased over 20 years.
In spite of the nonoperative treatment as conservative treatment such as parmacotherapy, physical therapy and intra-articular injection therapy, when no symptom improvement is observed and the change of the joint continuously proceeds in such a way as to impede leading of everyday life, operative treatment is conducted.
By appropriately selecting operative treatment depending upon the age and the state of the joint, satisfactory results can be obtained.
The operative treatment includes arthroscopy, osteotomy, chondrocyte transplantation, and arthroplasty. A serious patient must receive arthroplasty.
The indication of arthroplasty for arthritis is when a patient's leg is curved and the effect of a medicine immediately disappears and the patient feels a pain even after taking the medicine.
In arthroplasty which is currently and directly conducted by a surgeon, since bone milling is not precise, it is difficult to precisely insert an artificial joint. Also, due to the imprecise insertion of the artificial joint, various complications may arise, and because the lifetime of the artificial joint is not so long, inconvenience is caused in that it is necessary to conduct surgery again some time in the future.
Recently, due to the development of a material and a surgery technique, the lifetime of the artificial joint has been increased over 20 years, and unicompartmental arthroplasty is also conducted such that the knee is incised by only about 6˜7 cm and only a portion of the knee joint suffering from serious arthritis is replaced with an artificial joint.
The arthroplasty of the knee joint (which is the joint placed among the lower end of the femur, the upper end of the tibia, and the rear surface of the patella) is also called replacement arthroplasty, knee joint replacement or total knee replacement arthroplasty. The arthroplasty indicates the replacement of the original knee joint with an artificial joint made of faux metal, plastic or ceramic. Actually, the arthroplasty indicates the surgery of cutting the knee joint including the cartilage which covers the end of the bone, by about 8˜9 mm and inserting the artificial joint therein.
The existing arthroplasty is conducted in a manner such that a master surgeon conducts surgery by milling out the bone directly using surgery instruments including a surgical drill, etc. This approach requires a substantial amount of incision of the skin and the flesh, and the precise milling of the stronger bone and the minimization of the damage to the bone are important in conducting the surgery. However, in the case that master surgeon directly conduct surgery, since it is difficult to handle precisely the surgery instruments and mill precisely the bone, an excessive amount of the bone is likely to be damaged during the milling of the bone or surrounding tissue is likely to be damaged.
In order to cope with these problems, there has been disclosed a method for milling the knee joint using a robot, that is, knee joint arthroplasty using a robot, in which the path of a rotary type cutter mounted to the distal end of a position-changeable arm of a robot is controlled in conformity with the information inputted to a computer so as to mill sequentially the bone of the knee joint so that planes, to which an artificial knee joint, i.e., an implant is to be coupled, are formed on the bone.
FIG. 39 illustrates a cutting system which is used in a conventional knee joint milling method using a robot.
Referring to FIG. 39, a rotary type cutter 100 mounted to the distal end of a position-changeable arm of a robot has a head 110 which is formed with cutting edges on the circumferential outer surfaces and the distal end surface thereof and has a diameter of 7.8 mm and a shaft 120 which extends from the head 110 and has the shape of a round bar and a diameter of 2.3 mm. The proximal end of the shaft 120 is connected to a motor M which is installed on the distal end of the position-changeable arm of the robot. The circumferential outer surface of the shaft 120 is rotatably supported in a sleeve 130 which is secured to the housing of the motor M so that quivering or bending does not occur while the shaft 120 rotates. The head 110 is positioned out of the sleeve 130 so that the bone can be milled through the rotation of the head 110.
As shown in FIG. 40, the conventional knee joint milling method using a robot adopts a top down milling scheme in that the cutter 100 approaches the knee joint from the anterior side of the knee joint and is moved repeatedly along the locus indicated by the arrows so that the bone can be gradually milled level by level by the head 110.
However, although the conventional method and the system contribute to some extent to the improvement in the precision of the surgery, they suffer from defects as described below.
That is to say, in the conventional method and system for cutting the knee joint using a robot, the entire shaft 120 of the cutter 100 for milling the bone is supported by the sleeve 130, the head 110 of the cutter 100 has a large size, and the head 110 approaches the knee joint from the anterior side of the knee joint and is rotated while drawing the large locus only in a lateral direction so that the bone can be milled by the head 110. Because of these facts, in order to avoid interference or impingement between the sleeve 130 and the head 110 and the skin tissue of the human body, a substantial amount of the skin and the flesh should be incised.
Also, due to the rotation of the head 110 having the large size, it is difficult to properly protect the important tissue such as the periosteum attached to the bone, and serious damage to the bone can be caused. Moreover, because a substantial amount of foreign substance such as bone particles are produced during milling, a surgery condition is deteriorated, and as the bone particles are introduced into the surrounding tissue, an inflammation may be caused after conducting the surgery, which can lead to a sequela of the surgery.
Further, since the conventional method and system adopt the top down milling scheme in which the bone is gradually milled out level by level, a lengthy period of milling time is required and a surgery time is extended as well. Due to this fact, the patient can feel severe pain even after the surgery, and the recovery of the patient can be retarded.
In addition, while the conventional level to level milling method has a characteristic in terms of precision, the patient and the master surgeon who has performed the surgery cannot be satisfied only with the precision. In order to provide enough satisfaction, the patient can walk within several hours without feeling pain after the surgery is completed and the patient comes out of the anesthetic.
Meanwhile, the conventional minimal invasive replacement surgery by the direct surgery of a surgeon confers advantages in that the skin is incised to a lesser degree so that the damage to the muscle and soft tissue can be minimized. Nevertheless, since the surgery is performed in a narrow space, the tissue is excessively retracted and therefore is likely to be damaged. Also, due to the incision of the skin to the lesser degree, the field of view becomes narrow, and it is difficult to insert precisely the implant.